What "mass timber" means
Mass timber is engineered structural wood — cross-laminated timber (CLT) panels for floors and walls, glue-laminated (glulam) columns and beams — manufactured to tight tolerance in a factory and assembled on site like a kit. It is not stick framing scaled up: a five-ply CLT floor panel behaves structurally more like a two-way slab, and the projects proving the method are commercial towers, not houses.
Programme: timber’s strongest card
A mass timber structure erects dramatically faster than in-situ concrete — typically a floor every one to two weeks with a small crew and no propping, curing or formwork cycle. Milwaukee’s 25-storey Ascent topped out its timber structure in under a year with erection crews a fraction the size of a concrete gang. The catch: the speed is bought upstream. Fabrication requires a fully resolved model months before site start, and a missed delivery stalls an erection crew within hours. Timber rewards builders with strong design discipline and punishes late changes brutally.
Cost: closer than the folklore says
Frame-for-frame, mass timber usually prices above a concrete structure in markets with cheap concrete labour — but whole-project comparisons narrow the gap: lighter structure (roughly a fifth the weight of concrete) means smaller foundations and cranes, faster programme means lower preliminaries and earlier revenue, and the finished soffit can eliminate ceilings. Honest current answer: expect a structure premium in most Australian markets, partially or fully recovered at project level, with the balance depending on design efficiency and how much timber you leave exposed.
Fire: engineered, not assumed
Mass timber’s fire performance rests on char: thick sections char at a predictable rate and retain structural capacity, and elements are sized so the residual section survives the design fire. Codes now provide real pathways — including for tall buildings — but they demand engineering: encapsulation requirements, connection protection and sprinkler provisions all scale with height. Insurers remain the practical constraint; construction-phase insurance for large timber jobs requires early engagement and moisture/hot-works management plans that concrete jobs never need.
Carbon: the tender-winning argument
Timber structures typically carry substantially lower embodied carbon than equivalent concrete frames, and the biogenic carbon stored in the wood can push the structure toward carbon-neutral on paper. Two honesty requirements: the benefit depends on certified sustainable forestry and end-of-life assumptions, and it must be claimed with EPDs and traceable supply, not slogans — clients scoring carbon in tenders increasingly audit the claim.
The verdict
Choose timber when programme speed, weight, carbon or workplace quality carry real value on the project, and when your design can be resolved early and held stable. Choose concrete when the design will move late, spans and loads are heavy, the local concrete market is sharp, or insurance appetite for timber is thin. The winning builders treat it per-project — and many of the best current buildings are hybrids: concrete cores with timber floors, using each material where it is strongest.